A train, or any string of vehicles with one or more coupled trailers, usually requires communication between the coupled vehicles. The communication may consist of commands and status report.
Examples of commands include instructions to turn on or turn off lights, brakes or refrigeration units, instructions to operate an automated uncoupling mechanism between two of the vehicles, and requests for the recipient to send a status report.
Examples of a status report include the current temperature, the identification of the next scheduled stop, and whether or not a light bulb is burnt out.
Existing methods of conveying communication include electrical signals sent over wires, changes in air pressure in air hoses, and radio signals between transmitter and receiver.
There are situations where it is infeasible or undesirable to physically connect communication wires or hoses, so radio is often used. However, it is difficult to target radio signals to a specific vehicle in the train, if it is farther away than the vehicle adjacent to the sender, without interception by other vehicles in the same or any other train, so such communication usually requires the use of an addressing or other identification technique.
There is a need to provide for communication between vehicles in a train that requires neither of the direct connection of wires or hoses between the vehicles nor the addressing of radio communication.